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Ontogeny of vasoconstrictor neurohypophysial hormone function in rats
L K Kullama1, V Balaraman, J R Claybaugh
1Department of Pediatrics, Kapiolani Medical Center for Women and Children, John A. Burns School of Medicine, Honolulu 96826.
The American Journal of Physiology
|January 1, 1990
Summary
This study shows norepinephrine (NE) and vasopressin (AVP/AVT) receptor-mediated contraction in rat aortas develops early. NE sensitivity increases with age, while AVP/AVT sensitivity slightly decreases initially.
Area of Science:
- Physiology
- Developmental Biology
- Pharmacology
Background:
- Arginine vasopressin (AVP) and arginine vasotocin (AVT) are key regulators of vascular tone.
- Norepinephrine (NE) is a primary mediator of vascular contraction.
- Understanding the ontogeny of these contractile mechanisms is crucial for developmental physiology.
Purpose of the Study:
- To investigate the developmental changes in rat thoracic aorta contractility mediated by AVP, AVT, and NE.
- To compare the ontogeny of AVP/AVT-mediated contraction with NE-mediated contraction.
- To identify the receptor subtypes involved in AVP and AVT actions in developing aortas.
Main Methods:
- In vitro study using rat thoracic aorta segments from Sprague-Dawley rats at 2-3 days, 6-7 days, and 12 weeks of age.
- Cumulative dose-response curves for KCl, NE, AVP, and AVT were generated.
- Selective V1 vasopressinergic inhibitor, [d(CH2)5Tyr(Me)]AVP, was used to assess receptor involvement.
Main Results:
- Receptor-mediated contraction to NE, AVP, and AVT was present from 2 days of age.
- Sensitivity to KCl and NE progressively increased with age.
- Sensitivity to AVP and AVT showed a slight decrease in the first week, with no significant age-related increase by 12 weeks.
- AVP and AVT-mediated contractions were inhibited by the V1 antagonist, indicating V1-like receptor activation.
Conclusions:
- Vascular contractility mediated by NE, AVP, and AVT is established early in postnatal development.
- Differential ontogenetic patterns exist for NE versus AVP/AVT sensitivity in rat thoracic aorta.
- AVP and AVT likely act via a common V1-like receptor in the developing rat aorta.